1. Field of the Invention
The present invention relates to a recording apparatus that discharges ink from a recording head and performs recording, and a pattern forming method for detecting defective discharge of the recording head.
2. Description of the Related Art
In an ink jet recording apparatus, one of causes for quality deterioration of a recorded image is defective discharge of ink from the recording head. In a conventional method for detecting defective discharge from the recording head, a user records a test image (a defective discharge detection pattern) on a recording medium, and visually checks whether the recorded test image includes recording omissions due to the defective discharge. Recently, the recording apparatus has detected defective discharge by reading the recorded recording medium using an optical sensor attached to a carriage or a scanner unit instead of visual detection.
However, both the visual method and the method using the optical sensor have a common problem in that the occurrence of the defective discharge barely is detected when the defective discharge occurs at an end of a nozzle array of the recording head. That is, when the defective discharge occurs at the center of the nozzle array, a slit-like recording omission occurs in the test image, so that a user can easily detect the defective discharge. However, when the recording omission occurs at an end of the nozzle array, the recording omission does not appear as a slit-like recording omission generated at the center of the nozzle array, so that the user tends to misunderstand that the discharging state is normal. In addition, when a user wants to detect whether the defective discharge occurs at only a part of the nozzle array (a nozzle group), the operator records the test image using only a part of the nozzle array. In such a case, the similar problem occurs.
To solve the aforementioned problem, Japanese Patent Application Laid-Open No. 2002-86773 discusses a method that detects defective discharge of a recording head by differently recording a test image of both ends of a nozzle array and a test image of the center of the nozzle array.
The method discussed in Japanese Patent Application Laid-Open No. 2002-86773 can more easily detect the defective discharge at the ends of the nozzle array. However, when the defective discharge occurs at the ends of the nozzle array, the ends of the test image are missed. Therefore, in both cases of the visual method or the method using the optical sensor, there is a problem that a user hardly detects the defective discharge compared with the case where the slit-like recording omission is generated at the center of the test image. Particularly, when the optical sensor with a small number of effective elements is used, the defective discharge at the ends of the nozzle array is not detected correctly. The optical sensor having a large number of effective elements can record an image that becomes a position reference (e.g., a black point having about 1 millimeter (mm) diameter) on the recording medium, and acquire position information of the test image. However, the optical sensor having a small number of effective elements cannot acquire the position information of the test image. Therefore, even when the defective discharge occurs at the ends of the nozzle array, a user recognizes that an end of a discharging part is an end of the test image, and cannot detect the defective discharge at the end of the nozzle array.